Hi Martian,

Minefield alert!

First there are different dated versions of SAP, which get used more and more a year or 2 after their apparent date. There's a transition period when different accredited software providers update their software. I'm not sure if there's ever a dictat issued that says "From now on all official assessments must use version XXXX" or the older versions just go out of use. So most assessments are currently done using SAP2005. This itself is about to be updated with a set of amendments (including things like wood pellet boilers) and will be called SAP2005.08.

Once you have your version of SAP there are several assessment regimes which are used to feed data in to the calculation. The original is the FULL Assessment - using when doing submissions for building regs and and now "On sale" for new building EPCS. A full assesments requires all of the data to be entered and includes all calculated u values for each wall type, window values and sizes, ventilation rates, etc.

RDSAP was recently introduced as a cut down version of SAP which required a lot less input from the assessor to save costs for homeowners / landlords who are now required by law to get an EPC when selling or renting. The things that make most difference are investigated by the assessors and entered into the software. The rest of the inputs are derived from values researched by BRE. The full SAP calculation is still done behind the scenes but using derived not entered values. This is close enough to get within 5% of what a full SAP assessment could do - but in 1/4 of the time. RDSAP is now included in the appendixes of the SAP specification (Appendix S I think).

With regards to local housing stock - most of these would have been traditionally been assessed with a different assessment altogether - something even more cut down than RDSAP and used to give a basic indicator of the SAP score. These were used for reporting average stock scores and to ensure compliance with minimum SAP scores which are part of decent homes standards. These are sometimes referred to a level 0 surveys and basically involve sticking in the house type (semi, 3 beds) heating type, and a few other basic parameters such as cavity insulation, loft insulation etc and it derives most of the other inputs. These are again defaults based on typical values. These surveys have been made obsolete by the requirement to provide an RDSAP based EPC to prospective tenants.

So the answer to your question is - RDSAP (based on SAP2005) finally became available during spring 2007. It makes sense that any assessment of council stock done after that time should use it - as the EPC produced will also be valid for 10 years for rentals. It wasn't compulsory though - and won't be till Oct 08 when EPCs are required for rentals. So the council could still probably get an old level 0 survey done for reporting against their decent homes targets, (and may indeed have done), but for an extra few quid, they could get a full RDSAP based EPC instead. Any assessment done prior to mid 2007 would have most likely - but not definitely using SAP2005 level 0 surveys. Prior to about mid 2006 would have been using SAP2001 as SAP2005 was still rolling out. The key thing is you can use anything as long as you know that a SAP score of 100 for SAP 2001 isn't the same as 2005. There was a change to the way they were calculated and it's not a simple conversion. So any databases containing data from both versions will need to note which type of assessment was used.

Got it?

Simon